The present invention relates to a new and improved construction of a blocking mechanism for an impact or percussion fuze comprising a spring-loaded blocking sleeve lengthwise displaceable in the fuze housing and provided with at least one radially movable blocking body which can be brought into a position blocking the blocking sleeve in the fuze housing by means of a spring-loaded blocking bolt lengthwise displaceable within the blocking sleeve, the fuze housing having a recess in which there can engage the blocking body for blocking the blocking sleeve in a first position.
There is already known to the art from Swiss Pat. No. 328,118 such type blocking mechanism wherein equally there can be blocked the blocking sleeve in a blocking position preventing firing by blocking a transverse slide in that the blocking sleeve pushes the blocking balls into the first recess in the fuze housing. Upon firing of the projectile initially the blocking bolt slides towards the rear, and as a result the blocking balls are freed and the blocking sleeve due to its moment of inertia likewise can move rearwardly. After the projectile has departed from the barrel of the weapon the air resistance causes a deceleration and the blocking bolt and the blocking sleeve strive to again move back into their blocking position. A conical portion at the blocking bolt however presses the balls which have been pressed into the radial bores in the blocking sleeve again apart until they clamp at a shoulder of the fuze housing. Hence, the blocking sleeve remains blocked in the ready-for-firing position where the transverse slide is not prevented from shifting into the live or armed position. Upon impact at the target the firing pin is pressed into the detonator cap arranged in the transverse slide.
Now if the projectile with the unarmed fuze, i.e. with the transverse slide in the blocked position is dropped with the tail-end leading from a given height, for instance 5 meters, onto a hard surface (for instance during testing of the dropping safety of the projectile), then there occurs a brief deceleration in consequence of which the blocking bolt slides rearwardly and the balls are released for a moment. However, until such time as the blocking bolt has arrived at its rearmost position the deceleration is no longer effective and the blocking sleeve no longer strives to move out of its blocking position likewise towards the rear. The blocking bolt again returns to its original position and presses the blocking balls back again into the first recess. If, however, the fuze experiences a greater deceleration, for instance due to dropping of the projectile with its tail-end leading from a greater height onto a hard surface, for instance from a height of 10 meters, then it can happen that the blocking sleeve due to its moment of inertia slides rearwardly to such an extent that the balls pushed into the radial bores arrive in a lengthwise position between both recesses of the fuze housing. The blocking bolt then, upon its return movement, presses the balls against the wall of the fuze housing bore. Due to the resulting frictional forces the forward movement of the blocking sleeve brought about by the spring action is impeded. If the frictional forces are so large that the spring coacting with the blocking sleeve is no longer capable of overcoming such forces (for instance the quality of the surface may have become damaged due to the application of excessive loads during transport), then the blocking sleeve remains in this semi-armed position. Even though the slide is still prevented by the blocking sleeve from shifting into the armed position, nonetheless the transport safety of such a semi-armed fuze is markedly impaired. Now further tail-end falling of the projectile against a hard surface, for instance from a height of 1 meter, is sufficient to release the clamping action of the blocking balls due to the rearwardly moving blocking bolt and the blocking sleeve can slide rearwardly to such an extent until it is blocked in the armed position in that the balls arrive in the second recess i.e. behind the corresponding shoulder in the fuze housing bore. The slide is now free and moves into the armed position. Upon firing of the projectile the gunnery crew is in extreme danger, since the detonation occurs already in the weapon barrel or directly in front of the barrel mouth.